Clear description of the problem: When Microsoft Excel is open (and has the focus) the â€œScroll inactive windowâ€ feature does not work as it is supposed to. To be precise, when Excel is open, it does not allow scrolling any other inactive window. This a known Microsoft problem, which was supposedly fixed in version 1803, but it didn't.

Installing XMBC, made things a lot better, it worked great within Excel (i.e. scrolling to cells when writing a formula in the formula bar), but again some glitches are still present when scrolling inactive windows.

To make the issue as clear as possible, I have created 3 test cases to reproduce the problem.

Excel is a royal pain the the A*S. It has been a problem for longer than since 2016 in my experience but there is nothing I can do about it. Well no more than I am already doing. I'm afraid I gave up a long time ago trying to fix specific problems with Excel.

Having said that, I just tried your test case 1 here on my Windows 10 laptop (1803) and Excel 2016 (office professional, not 365) and it worked (with and without XMBC running) - I'm pretty sure it didn't work before so maybe something has changed in 1803?!

Telling the difference between two excel windows (test case 2) is impossible the way XMBC currently recognizes windows, because they are both the "same" process, the message gets sent to the focus window - when I tried anything else it the past, neither scrolled (which was definitely worse!).

I might have another play now MS seem to have changed things, but in reallity, its Excel that needs to change as it is only Excel that behaves in this very strange way, other MS and non-MS windows don't suffer this (often) which means Excel is breaking some windows message rules somewhere or other.

You're "luckier" I guess with Test 1, as with Edge I have the described problem with XMBC. Without XMBC, forget it... does not scroll anything when Excel is open!!
It seems that the combination, Excel/Edge is "deadly"!!!!!

Just FYI, Microsoft officially announced to have fixed the Excel problem in build 17133.73 build update on Apr-10, as well as latest Excel Monthly channel 1803 Build 9126.2152 update on Apr-11.

Unfortunately I have a Volume licensed Office ProPlus x64, version 16.0.4639.1000 and do not have the luxury of the Monthly channel, where in the above version the issue was fixed. (I'm talking about Test Cases 1 and 3, whereas 2 seems to be more difficult to cure, even for Microsoft)

I'm afraid, if MS have changed something in Windows 10 to fix this, then I suspect you are out of luck with Win 7!
XMBC is not able to fix it properly as I said before, this one has had me stumped for some time!